The present invention relates to the technical field of detecting contraband such as weapons, explosives, drugs, etc., in containers such as large cargo containers and small baggage. More particularly, the present invention is directed to an apparatus and process of non-intrusive x-ray inspection of containers through which contraband can be detected.
The transport of contraband has become and continues to be a worldwide problem. For safety, compliance of laws and other numerous reasons, it is desirable to inspect containers for establishing whether or not contraband is contained therein. Because it is impractical to open and physically inspect every container traveling through, for example, airports and harbors, it is desirable that the containers be inspected in a non-intrusive manner, that is, without opening and physically inspecting. Numerous attempts and devices have heretofor been suggested for accomplishing such non-intrusive inspections. Some such devices and/or components of such devices known to applicant are disclosed in the following references:
1. U.S. Pat. No. 5,442,672, August 1995;
2. Richard F. Eilbert and Kristoph D. Kug, SPIE Vol. 1824 (1992)/127-143;
3. U.S. Pat No. 5,319,547, June 1994;
4. U.S. Pat No. 5,490,218, February 1996;
5. U.S. Pat No. 5,600,700, February 1997;
6. U.S. Pat No. 5,642,393, June 1997;
7. Pratt R. H., Tseng H. K., Lee C. M. Atom. Data. Nucl. Data. Tables. 1977. O1. 20, No. 2.P. 175-209; and,
8. Russian Federation Patent No. 2115914, 23.04.1997.
Prior non-intrusive inspection apparatus and systems, however, are inaccurate and are thus impractical because they either are incapable of detecting contraband or can not distinguish between contraband and other materials, thereby passing over and not detecting contraband or mistaking other materials for contraband and causing false alarms.
Accordingly, a need exists for a more accurate cargo inspection apparatus and process through which contraband can more accurately be detected with minimal false alarms.
It is the principal object of the present invention to overcome the above-discussed disadvantages associated with prior cargo inspection apparatus and processes.
The present invention, in summary, is an apparatus and process through which cargo and baggage containers are scanned with x-rays along two different planes. While scanning along the first plane, a first sequence of one dimensional arrays from outputs of a plurality of x-ray sensors representative of a first x-ray intensity spectrum is obtained and a second sequence of one dimensional arrays from outputs of a plurality of x-ray sensors representative of a second x-ray intensity spectrum is also obtained. Similarly, while scanning along the second plane, a second sequence of one dimensional arrays representative of a first x-ray intensity spectrum and a second sequence of one dimensional arrays representative of a second x-ray intensity spectrum are also obtained. By using the first intensity spectrum and second intensity spectrum sequence of one dimensional arrays, atomic number sequences of one dimensional arrays are calculated for both the first and second planes. By combining at least one of the first plane first or second one dimensional arrays, a first plane image is provided. Similarly, by combing at least one of the second plane first or second sequence of one dimensional arrays, a second plane image is provided. A suspicious area and a background area are then identified in at least one of the first plane image or the second plane image. By using a representative suspicious area and representative background area geometry along with the atomic number and mass thickness values of the suspicious areas and background areas and by assuming that the effect of the background area is the same in the projection through the suspicious area, the background values are subtracted or otherwise compensated for in the suspicious area values for thereby effectively removing the background and calculating the more precise average atomic number and density of the suspicious contraband. Thereafter, the average atomic number and density of the suspicious contraband is compared with known atomic numbers and densities of actual contraband materials and a visual or audible output is provided indicative of whether the suspicious contraband falls within the parameters of actual contraband material.
Preferably, in addition to the first and second plane images, first and second plane atomic number display images are also provided for aiding in the identification of suspicious contraband. More preferably, the first and second plane atomic numbers display images provide a color display of the scanned container with the various materials corresponding to different groups of atomic numbers being displayed in different colors.
In one form thereof, the present invention is directed to a process of detecting contraband within a container. The process includes the steps of scanning the container with x-rays along a first plane and obtaining a first sequence of one dimensional arrays from outputs of a plurality of x-rays sensors representative of a first x-ray intensity spectrum. A second sequence of one dimensional arrays from outputs of a plurality of x-ray sensors representative of a second x-ray intensity spectrum is also obtained along the first plane. The container is further scanned with x-rays along a second plane and a second sequence of one dimensional arrays from outputs of a plurality of x-ray sensors representative of a first x-ray intensity spectrum is obtained. A second sequence of one dimensional arrays from outputs of a plurality of x-rays sensors representative of second x-ray intensity spectrum along the second plane is also obtained. By using the first plane first intensity spectrum and the second intensity spectrum sequence of one dimensional arrays, a first plane atomic number sequence of one dimensional arrays is calculated. By using the second plane first intensity spectrum and the second intensity spectrum sequence of one dimensional arrays, a second plane atomic number sequence of one dimensional arrays is calculated. A first plane image is then provided by combining at least one of the first plane first or second one dimensional arrays. A second plane image is also provided by combining at least one of the second plane first or second one dimensional arrays. A suspicious area and a background area are then identified in at least one of the first plane image or the second plane image. Using a representative suspicious area and background area geometry, along with the atomic number and mass thickness values of the suspicious areas and background areas, the average atomic number and density of the suspicious contraband is calculated. The average atomic number and density of the suspicious contraband are then compared with known atomic numbers and densities of actual contraband materials and an output is provided indicative or whether the suspicious contraband falls within the parameters of actual contraband material.